Patent GB-342712-A (GB)
Title: Improvements in or relating to dry spinning cellulose derivatives
IPC: D01F2/30
Filed: 1929-10-03
Abstract: <PICT:0342712/IV/1> Artificial filaments, threads, ribbons, &c. of fine denier and/or increased strength are formed by extruding solutions of cellulose acetate or other cellulose derivative into an evaporative atmosphere; applying to the filaments &c. after the formation of a skin-like outer layer thereon, e.g. when the filaments &c. contain 25-50 per cent of solvent, a liquid solvent or softening agent; and stretching and completing the setting of the products. The treatment with the liquid may follow the treatment with softening vapour described in Specifications 340,929 and 340,930. Softening-liquid is applied by a wick, bath, &c. and the softened product is stretched by a draw-roller &c.  Further stretching may be applied when the products have reached an elastic condition, as described in Specification 323,790, [Class 2 (ii), Cellulose &c.]. Setting is effected in a further evaporative atmosphere or by washing off the solvent or softening liquid by suitable diluents or by passing the filaments &c. through a suitable coagulating bath.  The stretch may be limited to the softened portion of the filaments &c. by passing the filaments &c., before or during the application of the softening liquid, over a roller guide or tension device offering resistance to their passage; a suitable tension device comprises two intermeshing "gates" of polished, steel bars, such gates being adjustable.  Suitable softening liquids are acetone alone or mixed with water or alcohol, acetic formic or lactic acids, acetyl acetone, dimethylethylene glycol, monomethyl- or monoethyl-ethyleneglycol, dioxane, methyl or ethyl lactate, diacetone alcohol, or mixtures thereof.  To facilitate stretching, plastifiers or high boiling solvents may be added to the spinning solution, e.g. for cellulose acetate, solvents such as cyclobutanone, acetyl-acetone, diacetone alcohol, dimethylethylene glycol, mono-methyl- or mono-ethyl-ethyleneglycol, or plasticizers such as ethyl xylene sulphonamides, may be used.  Suitable organic derivatives of cellulose are cellulose acetate, formate, propionate and butyrate; methyl, ethyl, and benzyl cellulose; and condensation products of cellulose and glycols or other polyhydric alcohols.  As shown, a 20-28 per cent solution of cellulose acetate in acetone containing, if desired, 5-20 per cent of diacetone alcohol or methyl or ethyl lactate, is extruded through a nozzle 2 into a cell 3, the filaments passing around a guide 4 over a conical feed roller 5 to a cap-spinning device 6 or other winding device.  The cell 3 is subdivided into compartments by partitions.  In the upper compartment 7 the skin-like layer is formed and the filaments pass through an opening 9 into the compartment 10 where they contact with wicks 11 supplied with softening liquid from tanks 12.  Suitable softening-liquids are 70 per cent aqueous acetone, 50 per cent alcoholic acetone, or 50-60 per cent aqueous or alcoholic dioxane, diacetone alcohol or methyl or ethyl lactate.  The softened filaments pass through an opening 18 to a final drying chamber 19.  Air &c. is admitted to the compartment 19 at 21 and passes through a pipe 22 to the compartment 7 and thence through an outlet 23 and main 24 to a solvent recovery plant.  The openings 9, 18 are preferably adjustable.  The air &c. may be introduced in the vicinity of the jet through ring &c. devices as in Specification 325,233, [Class 2 (ii), Cellulose &c.]; and collector devices as described in Specifications 300,998 and 326,232, [both in Class 2 (ii), Cellulose &c.], may be employed.  Specifications 198,023 and 203,092, [both in Class 2 (ii), Cellulose &c.], also are referred to.